A triple cysteine motif as major determinant of the modulation of neuronal K V 7 channels by the paracetamol metabolite N-acetyl-p-benzo quinone imine.

Background and Purpose: The analgesic action of paracetamol involves K _V 7 channels, and its metabolite N-acetyl-p-benzo quinone imine (NAPQI), a cysteine modifying reagent, was shown to increase currents through such channels in nociceptors. Modification of cysteine residues by N-ethylmaleimide, H ₂ O ₂ , or nitric oxide has been found to modulate currents through K _V 7 channels. The study aims to identify whether, and if so which, cysteine residues in neuronal K _V 7 channels might be responsible for the effects of NAPQI.
Experimental Approach: To address this question, we used a combination of perforated patch-clamp recordings, site-directed mutagenesis, and mass spectrometry applied to recombinant K _V 7.1 to K _V 7.5 channels.
Key Results: Currents through the cardiac subtype K _V 7.1 were reduced by NAPQI. Currents through all other subtypes were increased, either by an isolated shift of the channel voltage dependence to more negative values (K _V 7.3) or by such a shift combined with increased maximal current levels (K _V 7.2, K _V 7.4, K _V 7.5). A stretch of three cysteine residues in the S2-S3 linker region of K _V 7.2 was necessary and sufficient to mediate these effects.
Conclusion and Implication: The paracetamol metabolite N-acetyl-p-benzo quinone imine (NAPQI) modifies cysteine residues of K _V 7 subunits and reinforces channel gating in homomeric and heteromeric K _V 7.2 to K _V 7.5, but not in K _V 7.1 channels. In K _V 7.2, a triple cysteine motif located within the S2-S3 linker region mediates this reinforcement that can be expected to reduce the excitability of nociceptors and to mediate antinociceptive actions of paracetamol.
(© 2024 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.)